Lifestyle factors are associated with osteoporosis in lean women but not in normal and overweight women: a population-based cohort study of 1222 women

The aim of the present population-based cohort study was to evaluate the contribution of lifelong lifestyle factors to calcaneal and distal forearm bone mass in elderly women. We studied 1222 of the 1689 eligible home-dwelling women aged 70–73 years. Lifelong occupational and leisure time physical activity, calcium intake, smoking, alcohol intake and medical history were obtained by a self-completed questionnaire. Main outcome measures were broadband ultrasound attenuation (BUA) of the calcaneus and bone mineral density (BMD) of the radius measured once in 1997–1998. The women with BMI ≤ 25.1 kg m² had lower BUA (p < 0.0001) and radial BMD values (p < 0.0001) than women with higher BMI. Lifestyle factors associated with BUA in the leanest women were: low physical activity at work (RR 0.4; 95% confidence interval 0.2 to 0.8), low habitual exercise at the ages 30 years , 50 years and currently (RR 1.5; 1.0 to 2.4; RR 1.5; 1.1 to 2.6; RR 1.7; 1.1 to 2.7), poor mobility (RR 1.9; 1.2 to 3.0), coffee intake ≥ 5 cups/day (RR 1.7; 1.1 to 2.7), type 2 diabetes (RR 0.3; 0.1 to 0.9) and hypertension (RR 0.5; 0.3 to 0.8). Type 2 diabetes protected lean women from lower distal and ultradistal radial bone density (RR 0.3; 0.1 to 0.8; RR 0.1; 0.1 to 0.5). The selected lifestyle factors were not associated with lowered calcaneal or radial bone density in the higher categories of BMI. In conclusion, risk factors for lower calcaneal and radial bone density appear to be different among lean and normal/obese women. Lifelong recreational physical activity, low physical activity at work, type 2 diabetes and hypertension seem to be associated with increased bone density, while high coffee intake may increase the risk of lower bone density in lean elderly women. These factors are potentially modifiable, and intervention studies targeted at this risk category of women are needed.